Question

What is the color of the aluminum sulfate solution in water?
A.Green
B.Colorless
C.Pink
D.Blue

Answer 1

Hint:
The determination of the chemical components in a given sample is called Analysis. In chemistry, there are two types of analysis made:
Qualitative analysis – that involves the identification of the unknown substance.
Quantitative analysis – that involves the determination of the composition of a mixture.

Complete answer:
Step 1
Qualitative analysis, i.e., identification of an unknown substance is done by carrying out chemical tests with the help of reagents. A reagent is a chemical substance that reacts with another substance.
Alkalis are important laboratory reagents. When they are added to certain salt solutions characteristic colored precipitates of metallic hydroxides are formed by which a metal ion can be identified.
Step 2
When alkali is added dropwise to certain metal solution precipitation takes place. Analyzing the color and nature of the precipitate the metal cation can be identified.
Step 3
The salts of representative elements of the periodic table, i.e., the elements of Group 1, 2, and 13 to 17 are generally colorless, while those of the transition elements, i.e., salts of elements of Groups 3 to 12 are generally colored. Different colors of colored salts help in their identification during qualitative analysis.
Step 4
The colorless cations are :
Ammonium ion - \[NH_4^ + \]
Sodium-ion - \[N{a^ + }\]
Potassium ion - \[{K^ + }\]
Calcium ion - \[C{a^{2 + }}\]
Magnesium ion - \[M{g^{2 + }}\]
Aluminum ion - \[A{l^{3 + }}\]
Lead ion - \[P{b^{2 + }}\]
Zinc ion - \[Z{n^{2 + }}\]
The colorless anions are:
Chloride ion - \[C{l^ - }\]
Sulphate ion - \[S{O_4}^{2 - }\]
Carbonate ion - \[C{O_3}^{2 - }\]
Nitrate ion - \[N{O_3}^ - \]
bicarbonate ion - \[HC{O_3}^ - \]
Sulphide ion - \[{S^{2 - }}\]
Bromide ion - \[B{r^ - }\]
Acetate ion - \[C{H_3}CO{O^ - }\]
Hence, aluminum sulfate in aqueous solution will dissociate into aluminum cation and sulfate anion both of which are colorless.

So, the aqueous solution of aluminum sulfate will be colorless and option b) is the correct answer to the given question.

Note:
\[C{u^{2 + }}\] ions show blue color, \[F{e^{2 + }}\] ions show pale green color, \[F{e^{3 + }}\] ions are yellowish-brown color \[N{i^{2 + }}\] and \[C{r^{3 + }}\] are green in color, and \[M{n^{2 + }}\] ion is pink in color.